ira: Scale save/restore costs of callee save registers with block frequency

ira: Scale save/restore costs of callee save registers with block frequency

In assign_hard_reg(), when computing the costs of the hard registers, the
cost of saving/restoring a callee-save hard register in prolog/epilog is
taken into consideration. However, this cost is not scaled with the entry
block frequency. Without scaling, the cost of saving/restoring is quite
small and this can result in a callee-save register being chosen by
assign_hard_reg() even though there are free caller-save registers
available. Assigning a callee save register to a pseudo that is live
in the entire function and across a call will cause shrink wrap to fail.

2024-06-25  Surya Kumari Jangala  <jskumari@linux.ibm.com>

gcc/
	PR rtl-optimization/111673
	* ira-color.cc (assign_hard_reg): Scale save/restore costs of
	callee save registers with block frequency.

gcc/testsuite/
	PR rtl-optimization/111673
	* gcc.target/powerpc/pr111673.c: New test.